Instrumental versus Expressive violence

Something I just came across :
http://quizlet.com/7202935/criminology-chapter-10-main-ideas-flash-cards/

Difference between instrumental and expressive violence
-Expressive violence: acts that vent rage, anger, or frustration
-Instrumental violence: acts designed to improve the financial or social position of the criminal

And then we have

Degrees of murder
1. First degree
2. Second degree
3. Felony murder

In the Jodi Arias trial, if you suspect or believe Jodi is guilty, it is surely clear that this was “expressive violence”.

• Jodi was surely not trying to improve her financial position or her social position.
• Supposing she accomplished the aim of her alleged secret murder mission, the objective was surely for the mission to remain secret.
• The theft of Travis’ gun (supposing it was his gun) cannot have been designed to improve her financial position.

It seems to me that charging Jodi with Felony murder surely goes outside the intention of the law. The degrees of murder are meant to be mutually exclusive. Something is wrong here.

See also trial minutes and Women don’t kill unless